Image blur is a common problem in photography and has a variety of causes such as motion of the subject and focusing errors. However, one of the most common causes of image blur is camera shake by the operator. Human muscles naturally tremor or shudder at frequencies generally in the range of 4-12 Hertz. When a person is holding a camera, this hand shudder causes blur in the image. Blur caused by such human tremor is particularly noticeable with long exposure times or when using a zoom/telephoto lens capable of very long focal lengths. In efforts to reduce such blur, hand-held imaging devices, such as digital cameras and camcorders, generally employ some type of image stabilization system.
Such systems typically detect motion of the imaging device in some fashion and employ a means to counteract or compensate for the detected motion in order to stabilize the image and reduce blur. For example, in still cameras, motion is typically detected through use of a pair of piezoelectric or MEMs (micro-electro-mechanical) gyroscopes. Alternatively, camcorders sometimes employ an electronic method wherein motion is detected by comparing each frame of a scene to the previous frame.
Camera phones are one of the largest and fastest growing markets worldwide. Because camera phones are small and lightweight, they are typically hard to grip and operate as a camera. As a result, images taken with camera phones are particularly prone to blur caused by hand shudder. Unfortunately, while the above described approaches are effective at reducing blur, they are not ideal for camera phones as gyroscopes are relatively large in size and frame-to-frame image comparison requires power processing capabilities not generally available in phones. Additionally, the cost of such approaches is generally prohibitive for use in camera phones and low-priced high volume imaging devices.